V4L/DVB (7474): support key repeat with dib0700 ir receiver

This patch enables support for repeating last event when a key is holded
down with dib0700 devices. It works with rc5 and nec remotes.
It also fixes an annoying bug that floods kernel log with "Unknown key"
messages after each keypress. This happened because the driver was not
resetting infrared register after each poll so it kept polling last key
even if nothing was being pressed. Fixing this, (calling rc_setup after
each poll), permits to implement key repeat.

Signed-off-by: Filippo Argiolas <filippo.argiolas at gmail.com>
Signed-off-by: Patrick Boettcher <pb@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>